From a235abc1ef99d4f414a465e07fd19aeac28aa663 Mon Sep 17 00:00:00 2001
From: Sylvestre Ledru <sylvestre@debian.org>
Date: Tue, 11 Oct 2022 09:16:43 +0200
Subject: [PATCH] Only enable LTO for some archs

---
 debian/changelog |  6 ++++++
 debian/rules     | 19 ++++++++++---------
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/debian/changelog b/debian/changelog
index 05ac410e..6d32076d 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,9 @@
+llvm-toolchain-15 (1:15.0.2-2~exp5) experimental; urgency=medium
+
+  * Only enable LTO for some archs
+
+ -- Sylvestre Ledru <sylvestre@debian.org>  Tue, 11 Oct 2022 09:15:56 +0200
+
 llvm-toolchain-15 (1:15.0.2-2~exp4) experimental; urgency=medium
 
   * Only ship libbolt_rt_hugify.a & libbolt_rt_instr.a on amd64
diff --git a/debian/rules b/debian/rules
index 893d5afc..74e0c3b0 100755
--- a/debian/rules
+++ b/debian/rules
@@ -395,17 +395,15 @@ ifneq (,$(filter $(DEB_HOST_ARCH_OS),linux))
 	STAGE_2_CMAKE_EXTRA += -DLLVM_USE_PERF=ON -DLLVM_ENABLE_LIBPFM=ON
 endif
 
+LTO_ENABLE=no
 # Only enable it for archs supporting gold
 ifneq (,$(filter $(DEB_HOST_ARCH),$(BINUTILS_GOLD_ARCHS)))
-# armhf is not yet quite ready for Thin, it FTBFS
-# see https://buildd.debian.org/status/fetch.php?pkg=llvm-toolchain-8&arch=armhf&ver=1%3A8.0.1%7E%2Brc2-1%7Eexp1&stamp=1560334266&raw=0
-ifeq (,$(filter $(DEB_HOST_ARCH), armhf))
-# Use BOOTSTRAP_LLVM_ENABLE_LTO to make sure that it isn't used
-# when running stage1 with gcc
-# For now, disable ThinLTO usage because:
-# * LLVM_ENABLE_LTO doesn't work with gcc >= 9 (option not accepted)
-# * BOOTSTRAP_LLVM_ENABLE_LTO is producing some large binary
-#   See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=943623
+# LTO requires a bunch of memory. Don't do it everywhere
+LTO_DISABLE_ARCHS := i386 armhf s390x ppc64 x32
+ifeq (,$(filter-out $(LTO_DISABLE_ARCHS), $(DEB_HOST_ARCH)))
+	LTO_ENABLE=no
+else
+	LTO_ENABLE=yes
 	STAGE_2_CMAKE_EXTRA += -DLLVM_ENABLE_LTO="On"
 endif
 endif
@@ -477,6 +475,7 @@ preconfigure:
 	@echo "PATH=$(PATH)"
 	@echo "LD_LIBRARY_PATH=$(LD_LIBRARY_PATH)"
 	@echo "LIBFUZZER_ENABLE=$(LIBFUZZER_ENABLE)"
+	@echo "LTO_ENABLE=$(LTO_ENABLE)"
 	@echo "COMPILER_RT_WASM_ENABLE=$(COMPILER_RT_WASM_ENABLE)"
 
 	for f in debian/*.in; do \
@@ -822,8 +821,10 @@ override_dh_auto_install:
 	# Clean up temporary files to make sure the install works
 	rm -rf $(find $(TARGET_BUILD) -wholename '*CMakeFiles*' -not -name CMakeLists.txt -a -name "*.dir" -type d)
 
+ifeq (${LTO_ENABLE},yes)
 	# with LTO, .a contains llvm ir instead of native code. So, recompile them
 	NJOBS="$(NJOBS)" P_TO_LLVM="$(CURDIR)" VERSION=$(LLVM_VERSION) bash debian/llvm-compile-lto-elf.sh $(CXXFLAGS_EXTRA)
+endif
 
 	# install/fast enables a make install without recompiling temporary files
 	LD_LIBRARY_PATH=$(STAGE_2_LIB_DIR):$$LD_LIBRARY_PATH DESTDIR=$(DEB_INST)/ ninja -C $(TARGET_BUILD) $(VERBOSE) stage2-install